Exposure to ionizing radiation has detrimental effects on tissues; and exposure of hemopoietic cells to such radiation, may provoke life threatening consequences. Radiation therapy is an important regimen of many anticancer treatments, together with chemotherapy, where cytotoxic effects of both these therapies often affect hemopoiesis. Therefore, protecting agents could substantially improve the efficiency of current anticancer therapies, in addition to their possible use in cases of accidental irradiation. Radiotherapy is a treatment for cancer and other diseases that incorporates ionizing radiation to destroy malignancies. Ionizing radiation damages or destroys cells in the area being treated, preventing the malignant cells from continuing to grow and multiply. Most radiotherapy techniques employ high energy X-rays or sometimes Gamma rays. In some instances internal radiotherapy (e.g. radioactive implant placed inside the body) may be used.
Radiotherapy can damage normal cells as well as cancer cells, and there may be potential side effects, which would depend on the radiotherapy dose, site(s) of treatment, age and other factors. The side effects of radiation therapy include temporary or permanent loss of hair in the area being treated, skin irritation, temporary change in skin color in the treated area, and tiredness.
Since radiation therapy can be and often is used in combination with chemotherapy or surgery, other common side effects as fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores may worsen the patient's condition and also increase the patient's discomfort.
One of currently used protections against radiation damages is the transplantation of bone marrow or administration of peripheral blood stem cells in early days post irradiation or chemotherapy. However, the hematopoietic stem cells recover to only 5% to 10% of normal levels after bone marrow transplantation [Mauch P. et al.: Blood (1989) Vol. 74(2):972; Thorsteinsdottir U. et al.: Blood (1999) Vol. 94 (8):2605], and recovery time is too long [Vellenga E. et al.: British J. Haematol. (1987) Vol. 65(2):137], not mentioning the problems of bone marrow storage [Soderdahl G. et al.: Bone Marrow Transplant (1998) Vol. 21(1):79].
The ability to modulate differentiation and proliferation of hematological precursors is at the basis of the more innovative therapies such as peripheral blood stem cell transplant, gene transfection and ex vivo expansion of stem cells. In spite of this impressive progress, several aspects of stem cell physiology have not been fully clarified.
Several factors are suspected of being involved in the physiological or pathological proliferation/differentiation of bone marrow cells. In addition to the role of classically defined growth factors, several biological agents and cell types could improve or modify both in vivo and ex vivo therapeutic strategies. Human bone marrow-derived endothelial cells support long term proliferation and differentiation of myeloid and megakaryocytic progenitors [Rafii, S., et al., Blood (1995) Vol. 86:353]; accessory cells may support hematological recovery after bone marrow transplant [Bonnet, D., et al., Bone Marrow Transpl. (1991) Vol. 23:203].
Short peptides have been synthesized to reach hemoregulatory and multilineage effects, possibly by enhancement of cytokine production by stromal cells [King, A. G., et al., Exp. Hematol. (1992) Vol. 20(4):531; Pelus, L. M., et al., Exp. Hematol. (1994) Vol. 22:239].
For example, the osteogenic growth peptide (OGP) was shown to induce, in vivo, a balanced increase in white blood cell (WBC) counts, and overall bone marrow cellularity in mice receiving myeloablative irradiation and syngeneic or semiallogeneic bone marrow transplants [Gurevitch, O., et al., Blood (1996) Vol. 88(12):4719].
Therefore, substances that can induce increment in colony forming units (CFU) capacity of bone marrow cells and related cells along the different differentiation paths, should find clinical application in treatments intending to restore the hematopoietic cells damaged by chemotherapeutic agents and/or radiation.
Oligopeptides that support hemopoiesis may prove useful in other ways as well. Some investigators have found that adding stem cells from peripheral blood to those from bone marrow significantly increases the rate of engraftment. However, extracting sufficient numbers of stem cells from peripheral blood is a complicated procedure. Administering such oligopeptides to donors to increase the number of stem cells in the blood will improve the feasibility of transplanting stem cells from peripheral blood [Golde, D. W., Sci. Am. (1991) Vol. 36 (December)].
The capacity of the hematopoietic stem cells to provide for the lifelong production of all blood lineages is accomplished by a balance between the plasticity of the stem cell, that is the production of committed progenitor cells which generate specific blood lineages, and the replication of stem cell in the undifferentiated state (self-renewal). The mechanisms regulating hematopoietic stem cells plasticity and self-renewal in vivo have been difficult to define. However, the major contributory factors represent a combination of cell intrinsic and environmental influences [Morrison, et al., Proc. Natl. Acad. Sci. USA (1995) Vol. 92:10302].
A prerequisite for hemopoiesis and therefore successful BMT is the presence of functional stromal cells and tissue that form part of the hemopoietic microenvironment, determine the homing of the injected stem cells from the circulation to the bone marrow and support hemopoiesis [Watson, J. D. and McKenna, H. J. Int. J. Cell Cloning (1992) Vol. 10:144]. Growth of bone marrow cells is supported by the stromal tissue. The tissue components provide the conditions needed for the survival of stem cells in long-term in vitro bone marrow cultures. At present this technology suffices to keep stem cells alive. Adding an appropriate factor, e.g. a “hemopoietic” oligopeptide to these cultures may help expand the stem cell population ex vivo/in vitro, thus providing increased numbers of these cells for transplantation.
A combined in vitro/in-vivo approach may provide the basis for a forward-looking strategy for (i) obtaining small stem cell preparations from donors of blood or marrow and (ii) enabling healthy individuals to have their stem cells stored for any future therapeutic need, thus bypassing the complexity associated with the use of allogeneic BMT.
It would therefore be of therapeutic importance to use small peptides such as the oligopeptide described in the present application, that stimulate post-BMT hemopoietic reconstruction by enhancing in vivo, ex vivo and/or in vitro the progenitor hemopoietic cells.
A largely used protective agent is amifostine [Merck Index, 12th Ed.], a thiophosphate developed by the US army as a radioprotective agent, and currently used to decrease the cytotoxic effects of both radiation therapy and chemotherapy. Amifostine must be administered shortly before irradiation; once reconstituted, its stability at room temperature is quite limited [Gosselin T. K. and Mautner B.: Clin. J. Oncology Nursing (2002) Vol. 6:175]. Most patients are afflicted by some of many side effects of amifostine, which include, e.g., hypotension, allergies, nausea and vomiting, the latter two occurring in approximately 53% of patients [Gosslin and Mautner, Ibid.].
The development of a non-toxic selective protective agent that preferentially protects normal tissues from chemotherapy toxicity, without protecting malignant tissues, is a major challenge in cancer chemotherapy research. The available protective agents are either toxic or lack selective protective activity.
It is therefore an object of this invention to provide a new protective agent, conferring protection to a tissue or body exposed to a cytotoxic factor, such as ionizing irradiation or cytotoxic chemical.
The tortoise is a quite remarkable animal in that it can survive a dose of ionizing radiation greater than other vertebrata, and nearly 100-times greater than mammals (Table 1) [Khamidov D. K. et al.: Blood and Haemopoiesis of Vertebrates with Radiation Injuries, Monograph, Tashkent (1986), “FAN” 175 pp.].
TABLE 1Lethal doses of ionizing radiation for different animalsAnimalLethal dose - LD50/30 (Gy)Golden fish25Frog15Lizard25Tortoise500Pigeon15Mouse7
EP 0377044 B1 describes a protective effect of a nonapeptide (EAKSQGGSN) on irradiated mice. U.S. Pat. No. 5,866,160 describes a composition of soft-shelled turtle and tortoise, for enhancing the leukocyte number in patients undergoing chemotherapy. Russian Patent RU 2118533C1 describes an extract from tortoise liver for improving hematopoietic function in irradiated mammals, and for increasing their viability. Jacobson [Jacobson L. O. et al.: Proc. Soc. Exptl. Biol. Med. (1950) Vol. 73:455] demonstrated an important role of spleen by screening the said organ during irradiation of mice, and finding that their survival rate significantly increased.
It was found that intraperitoneal injection of tortoise plasma increased the survival rate of mice after whole body γ-irradiation (8 Gray; Gy) and that the injection of a spleen extract had a still stronger effect [Turdiev A. et al.: Radiobiology (1985) Vol. 25:655; Turdiev A. et al.: Radiation Biology and Radioecology (1998) Vol. 38:63].
It is therefore another object of this invention to provide a new protective agent conferring protection to a tissue or body exposed to a cytotoxic factor, such as an ionizing irradiation or a cytotoxic chemical, wherein said protective agent is derived from tortoise spleen.
It is further an object of this invention to provide a pharmaceutical composition comprising a factor or oligopeptide derived from tortoise spleen, that can decrease damages caused by an ionizing irradiation to a tissue or body, wherein said irradiation is either accidental or a part of radiation therapy.
It is a still further object of this invention to provide a pharmaceutical composition comprising a factor or oligopeptide derived from tortoise spleen that can decrease damages caused to a tissue or body by an exposure to a cytotoxic chemical, wherein said exposure is either accidental or a part of chemotherapy.
Other objects and advantages of present invention will become apparent as description proceeds.